The present invention relates to the structure and method for forming connector terminal electrode films of a lamination capacitor on the side of a ceramic main body part and connected to internal electrodes inside the main body part.
Referring to FIGS. 1 and 2, a lamination capacitor consists of a parallelepiped ceramic main body part 1 containing first and second pluralities of internal electrodes 2 and 3 arranged in alternating layers. Internal electrodes 2 are displaced in main body part 1 such that they are exposed at a face 1a. Similarly, internal electrodes 3 are displaced in main body part 1 such that they are exposed at a face 1b. A connector terminal electrode film 4 is coated on face 1a of main body part 1 to make contact with the exposed ends of internal electrodes 2. A similar terminal electrode film 4 is coated on face 1b of main body part 1 to make contact with the exposed ends of internal electrodes 3.
Japanese Unexamined Patent Publication No.SHO 60-236207 (236207/1985) discloses a three-layer structure having terminal electrode films 4 affixed by conductive adhesive to faces 1a and 1b to form first electrode layers 4a. A second electrode layer 4b of a solder-heat-resistant metal such as, for example, nickel or copper, is coated on a surface of first electrode layer 4a by any convenient method such as, for example, sputtering, vacuum evaporation or plasma spray coating. A third electrode layer 4c of a soft-solderable metal such as, for example, tin or silver, is coated on a surface of second electrode layer 4b by any convenient method such as, for example, sputtering, vacuum evaporation or plasma spray coating.
Since first electrode layer 4a of terminal electrode film 4 is affixed by coating conductive paste directly onto the faces 1a and 1b of the main body part 1, the thickness of the first electrode layer 4a of conductive paste is relatively large and not uniform. Thus the length L of a lamination capacitor is increased and its dimensional uniformity is poor.
Besides coating conductive paste on faces 1a, 1b of the main body part 1, the conductive paste also coats the top 1c, bottom 1d and the left and right sides 1e, 1f of the main body part 1. It is difficult to maintain a constant thickness of conductive paste on these top 1c, bottom 1d, left 1e and right sides 1f. Thus, the height H and width W of a lamination capacitor made according to the prior art are larger than necessary and the dimensional precision of these dimensions is not as precise as desired.
A part of the relatively thick terminal electrode film 4 extends over the top 1c, bottom 1d, left 1e and right sides 1f of the main body part 1. Thus when a lamination capacitor is held by a vacuum collet for automatic installation onto a printed board of an electrical appliances the present of the thick terminal electrode film 4, extending to the top surface 1c of the main body part 1, sometimes interferes proper manipulation of the lamination capacitor by the vacuum collet.
Because of the manner in which coating must be done, terminal electrode films 4b and 4c generally cover most, of not all, of main body part 1. In order to make the device useful, the unwanted material must be removed from sides 1c-1f by, for example, etching. This adds substantially to the cost of manufacture, and to the scrap rate.